For example, a mobile phone is in a standby state while it is supplied with power. The mobile phone can receive incoming calls from other phones. To receive incoming calls, the mobile phone needs to report a present paging area, where the mobile phone is present, via a base station to a location registration DB of a base station controlling station. The base station controlling station controls multiple base stations that form wireless areas as paging areas.
On receiving the report from the mobile phone, the base station controlling station stores and registers the mobile phone number in the location registration DB, in association with the paging area information. The base station controlling station notifies the mobile phone that its mobile phone number has been stored in the location registration DB in association with the paging area information, via the base station.
In particular, the mobile phone sends a location registration message to the DB via the base station. When the mobile phone receives a receipt acknowledgement (so-called ACK signal) of the message, the mobile phone determines that the location registration is complete. Then, the mobile phone stores information about the paging area, where the corresponding location registration is done, in its volatile memory device (hereinafter called a RAM).
Through these processes, the base station controlling station can specify which mobile phone is present in which paging area out of the multiple paging areas. The mobile phone can recognize the paging area from which the mobile phone receives incoming calls. These processes are generally called a location registration.
For example, a mobile phone makes a call, and there is an incoming request for a certain mobile phone which has registered its location in the base station controlling station. The base station controlling station notifies the paging area where the location of the certain mobile phone is registered, that there is an incoming request, by use of a paging channel. Accordingly, the certain mobile phone can receive the call and perform communications.
When entering a new communications area, the mobile phone receives information of a new paging area. The mobile phone determines whether the new paging area matches the paging area stored in the RAM. When the new paging area does not match, the mobile phone notifies the base station controlling station of a location registration message, which shows that the mobile phone is present in (moves to) the new communications area, via a base station. The mobile phone updates the information stored in its own RAM by using the new paging area where a new location registration is done. Accordingly, the mobile phone can perform communications anywhere in wireless areas.
The mobile phone has a power supply button (or switch) which can turn on or off the power supply, and for example, the power supply can be turned off on a train or in a hospital if necessary. When the user turns off the power supply of the mobile phone, a control device of the mobile phone writes information about the paging area stored in the RAM (hereinafter also called RAM-storing information), in a nonvolatile memory device (EEPROM) of the mobile phone. The control device then turns off the power supply for the mobile phone.
When the user presses the power supply button to turn on the power supply again, the control device receives new paging area information sent from the base station controlling station via a base station. The control device writes the information about the paging area which is stored in the EEPROM (hereinafter also called EEPROM-storing information), in the RAM. The RAM-storing information is thus returned to the state just before the power supply is tuned off.
The control device of the mobile phone compares the paging area information in the RAM with the paging area information received after the power supply is turned on. When the control device of the mobile phone determines that both do not match each other, the control device does a location registration with the base station controlling station via the base station. When the control device determines that both match each other, the mobile phone enters a state of waiting for incoming calls without doing the location registration. Accordingly, the redundant location registration can be avoided in the same paging area.
As a result, every time the power supply of the mobile phone is turned on and off, the redundant location registration can be avoided. This reduces loads in the communications with the base station controlling station via the base stations for the location registration. The writing in the EEPROM is executed only when the power supply is turned off. The number of the writings in the EEPROM can be small in comparison with the case where the writing is executed every time the paging area information in the RAM is updated. As a result, a longer time to reach the limit of the number of the writings in the EEPROM of the mobile phone leads to a longer life span of the mobile phone.
In recent years, vehicular wireless apparatuses have appeared. For example, use of a vehicular wireless apparatus provides the following: a remote car security function for reporting that a vehicle has been broken into even when the driver is away from the vehicle; an emergency report function for communicating with an outside in case of a contingency such as a traffic accident; and a guide function for obtaining congestion information or guide information about shops the driver wants to visit from an outside via communications.
For example, the car security function requires continuous communications even when the driver is away from the vehicle. Even when an ACC switch of the vehicle is off, the vehicular wireless apparatus needs to communicate with an outside of the vehicle.
As a result of the inventors' examination of this apparatus, the following operations are found. For example, regardless of whether the ACC switch of the vehicle is on or off, a control device of the vehicular wireless apparatus determines whether received new paging area information is different from RAM-storing information about the paging area (i.e., RAM-storing paging area information). When the new paging area information is different, the location registration is done as described above, and the paging area information in the RAM is updated to the new paging area information. The control device of the vehicular wireless apparatus does not update the paging area information in the EEPROM. These operations are the same as the above mobile phone.
The inventor has installed a power-on-rest in the whole of the vehicular wireless apparatus to stabilize; the power-on-reset runs when the user turns the ACC switch from off to on.
The RAM-storing paging area information of the vehicular wireless apparatus is reset by the power-on-reset and disappears. Accordingly, a location registration is newly done after the power-on-reset even though the paging area does not change actually.
Regarding the mobile phone, user's turning off the power supply button becomes a trigger of writing or duplicating the RAM-storing paging area information in the EEPROM. In contrast, the vehicular wireless apparatus does not have such a trigger.
Accordingly, with or without a change of the paging area information after the power-on-reset operated when the ACC switch is turned on, a location registration is newly done.